Physiological studies on Phymatotrichum omnivorum. IX. Synthesis of indole acetic acid in vitro.

The cotton root rot fungus, Phymatotrichum omnivorum, synthesized indole acetic acid (IAA) in culture medium containing tryptophan as the only source of nitrogen. Synthesis of IAA was not affected by illumination, and maximum amounts of the auxin were produced at 30 days. The optimum hydrogen ion concentration and temperature for IAA production were 6.5 and 28 degrees C, respectively. Indole ethanol (IEA) was also detected in tryptophan media, primarily during the active growth of the organism.